Cannulae-flushing means

ABSTRACT

To prevent the clotting of blood in small drainage tubes, or socalled cannulae, placed in the blood vessels of hospital patients for the purpose of monitoring the patients&#39;&#39; blood pressure there is provided an apparatus adapted to support a hypodermic syringe in position to direct a flushing solution into a cannula at periodic intervals, said apparatus including a motor-driven cam and coacting spring-loaded plunger mechanism for evacuating and refilling said syringe and adjustable timing means operatively associated therewith designed to automatically energize said mechanism at desired preset time intervals.

I United States Patent [i113,534, 23

[72] inventor Robert P. Carlisle 3,142,298 7/1964 Koski et al. 128/276 1614 North 119th St., Milwaukee, Wis. 3,335,724 8/1967 Gienapp r 128/218 53226 3,429,313 2/1969 Romanelli 128/276 2 1 1968 Primary Examiner-Dalton L. Truluck 1 I e Attorney- Morsell and Morsell [4S] Patented June 15, 1971 [54] CANNULAE-FLUSHING MEANS 1 Claim, 4 Drawing Figs.

[52] U.S. C] 128/2.05R, ABSTRACT: To prevent the clotting f blood i Small 123/218"! 128/2761 222/148 drainage tubes, or so-called cannulae, placed in the blood ves- [51] Int. Cl A6lb 5/02, Sels of hospital patients for the purpose of monitoring the A6lm 5/20 tients blood pressure there is provided an apparatus adapted [50] Fleld of Search 128/2, 2.05, to Support a hypodermic syringe in position to direct a flushing 1731 232/148: solution into a cannula at periodic intervals, said apparatus in- 239/106 eluding a motor-driven cam and coacting spring-loaded 1 plunger mechanism for evacuating and refilling said syringe [56] References Cited and adjustable timing means operatively associated therewith UNITED STATES PATENTS designed to automatically energize said mechanism at desired 3,042,042 7/1962 Blanck 128/276 preset time intervals.

PATENTEI] JUN! 5 mm SHEET 1 BF 2 INVENTOR OBERT P. CARLISLE ATTORNEYS PATENTED JUN] 5191:

SHEET 2 BF 2 1% Mia.

INVENTOR ROBERT P. CARLISLE ATTORNEYS CANNULAE-FLUSZ-IING MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the art of flushing cannulae to prevent blood clots from forming therein.

2. Description of the Prior Art Patients in intensive care units and coronary care units, as well as in recovery wards of hospitals, often require direct blood pressure monitoring, either venous or arterial. For this purpose cannulae must be temporarily placed in the patients blood vessels. Unfortunately, blood tends to form clots within the passageways, or so-called lumen, of such cannulae, and while venous cannulae can be kept unobstructed by a continuous drip maintained by hydrostatic pressure, arterial cannulae cannot be maintained in this manner.

In order to maintain an open lumen or passageway in arterial cannulae such'cannulae have to be flushed periodically, as for example at to minute intervals. The conventional practice is for the nursing personnel to perform this operation, which is a tedious chore as well as disturbing to the patient. In a centrally monitored ward, moreover, where the blood pressure monitoring equipment is in the nurses station, the nurses have to continually leave their station in order to flush the system, thereby reducing the effectiveness and efficiency of patient care. In addition, if a nurse should become busy and forget to flush the system for even a short period beyond the specified time the cannulae invariably becomes clogged and must be removed from the artery.

I-Ieretofore no one has devised an apparatus for the purpose of automatically flushing cannulae at variable predetermined intervals to prevent blood from clogging therein. Motor-actuated syringes have been the subject of numerous prior patents, but none of said prior devices has been like the present invention in either purpose or structure. Examples of such earlier inventions are disclosed in the following U.S. Pat. No. 3,336,925; No. 3,156,236; No. 3,335,724; No. 2,896,621; No. 2,457,977; No. 3,313,291; No. 2,602,446 and No. 2,498,672.

SUMMARY OF THE INVENTION The present invention comprises a novel apparatus which is designed to automatically periodically flush cannulae in the blood vessels of a patient in order to prevent blood from clogging therein, said apparatus eliminating the job of manually performing such cannulae-flushing operation. The result is the elimination of a task that is not only tedious and time consuming, but which necessitates a nurse leaving other important duties every few minutes to perform.

A further object of the present invention is to provide an automatic cannulae-flushing apparatus as described which eliminates the necessity for repeatedly disturbing a patient during the flushing operation, as is required with the conventional, manual procedure.

A further object of the invention is to provide a novel cannulae-flushing apparatus that can be utilized to simultaneously flush a plurality of cannulae in one or more patients.

A further object is to provide a cannulae-flushing apparatus wherein the volume of flushing fluid discharged cyclically can be adjusted to correspond to the requirements of the particular patient, thereby permitting the use of the device with either adults or small children.

A further object is to provide a cannulae-flushing apparatus wherein minimal blood pressure distortion is present, thereby promoting accuracy in monitoring vascular pressures, and wherein the use of undesirable anticoagulants is unnecessary.

A further object of the invention is to provide a novel automatic cannulae-flushing apparatus as described which is designed to use standard sterile disposable plastic syringes and conventional plastic tubing such as are readily available in hospitals, thereby minimizing costs.

A further object is to provide a novel cannulae-flushing apparatus having an air-free collapsible reservoir which effectively prevents the inadvertent introduction of air into the system when said reservoir becomes empty.

A further object is to provide an electrically operated cannulae-flushing machine wherein only the surface of the plastic syringe contacts the operating mechanism, thereby eliminating the possibility of electric current being accidentally transmitted to the patient.

Still further objects of the present invention are to provide a new and improved apparatus for automatically flushing cannulae, as described, which apparatus is relatively simple in design and operation, which is rugged and durable in construction, and which is otherwise particularly well adapted for its intended purposes.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, wherein the same reference numerals designate the same or similar parts in all of the views;

FIG. 1 is a side elevational view of the novel cannulae-flushing apparatus;

FIG. 2 is a top plan view of said apparatus;

FIG. 3 is a fragmentary view looking at the underside of the apparatus, said view being talten along line 3 3 of FIG. 1; and

FIG. 4 is a simplified circuit diagram of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawings, the complete assembly comprising the present invention includes an electrical switch 10 (FIG. 1 and 2) which is operably associated with a magnetic clutch 11 (FIG. 3) forming a part of a timing unit including a timing motor mounted in a housing 12 (FIG. 2). In one preferred embodiment of the invention said motor is 96 r.p.m., v., 60 cycles, 5 watts, but it is to be understood that these specifications are by no means critical and the invention is not to be limited in this respect.

As best appears in FIGS. 11 and 3, operatively associated with the timing motor 12 and with the magnetic clutch 11 is a calibrated dial 13 which can be manually rotated and set for a desired time interval. In one preferred embodiment of the invention the time setting is adjustable between 1 and 6 minutes. The periphery of said dial 13 is serrated and is adapted to releasably retain the hooked end of a pivotal and extensible spring-loaded arm 14 (FIG. 3), said hooked arm end being designed to engage on said serrated dlial edge when the magnetic clutch llll is energized, to draw said arm inwardly into contact therewith. In the operation of the apparatus, as the dial 13 turns with the timing motor said arm 14 moves axially inwardly, in the direction of the arrow in FIG. 3, until the specified time period has elapsed. At that moment said arm 14 trips a microswitch 21 (FIG. 4) which initiates a relay 22 (FIGS. 2 and 4), as well as resetting the timing motor.

It is to be understood that while the above-described form of timing device has proven satisfactory, other comparable adjustable timing means could also be employed. The reason a relatively wide timing range (1 to 6 minutes, or more) is desirable is because if it is a venous line that is being purged of blood clots it is not necessary to flush the same as often as is required for an arterial line, because there isnt as much backup pressure. With an arterial line, on the other hand, the relatively high pressure head tends to fill up the line with blood which coagulates to block the tip of the syringe needle, thus necessitating more frequent flushing.

With reference again to FIG. 2 of the drawings, operatively associated with the above-described timing means is a drive motor (not shown) mounted in the housing 23. A 10 r.p.m. motor has been found to provide excellent results, but any suitable motor could be utilized. Carried on the outer end of the motor drive shaft 24 is an enlarged cam 25 (FIGS. l and 2), hereinafter referred to as the driving cam, and also mounted on said motor shaft is a second, so-called shutoff cam 31 which is engageable with a microswitch 32. As will be hereinafter described in greater detail, said cam and microswitch assembly 31, 32 is adapted to turn off the motor 23 after each operational cycle.

Positioned forwardly of the driving motor and cam assembly is a rigid rectangular supporting block 33, there being an upwardly and rearwardly angled plate 34 secured thereto and supporting the aforementioned switch 10, as well as a light 35 designed to give a visual indication when the machine is turned on. In addition, said plate 34 carries an auxiliary pushbutton switch ill, the function of which will be hereinafter seen.

The complete unit comprising the present invention is mounted on a flat base member to which is preferably formed of stainless steel in order to promote sanitation, and a stainless steel cover or housing fits over the entire apparatus to provide a neat and attractive unit. Said housing has been omitted in the drawings, however, in order to provide a clearer showing of the working mechanism.

Referring still to FIGS. 1 and 2 of the drawings, the rectangular supporting block 33 mounted on the base 16 has a pair of spaced horizontal bores 42 formed therethrough, and axially slidably projecting through each of said bores is a rod 43. The rearward ends of said rods 43 are secured to an elongated crossbar 44, and projecting rearwardly from the latter intermediate its length is a roller 45 engageable with the aforementioned driving cam 25.

As best appears. in FIG. 2, the opposite ends 43 of said slidable rod members 43 have enlarged intumed flanges designed to engage the head ends of plungers 50 slidably mounted in and projecting rearwardly from conventional plastic syringes 51, said syringes and plungers being shown in dot and dash lines. The syringes 51 are removably retained in a rectangular holder 52 mounted adjacent the forward edge of the base 16, said holder having a hinged top member which is held in syringe-clamping position by means of a pivotal bolt and wing nut assembly 53. Said syringes i are positionable in communication with a pair of cannulae (not shown) in one or more patients blood vessels for the purpose of flushing said cannulae to prevent blood clots from forming therein. While a dual-syringe unit of the type illustrated has been found to provide an efficient arrangement, the holder could also be designed for a single syringe, or for three or more syringes, depending upon the intended use of the unit.

As shown in FIG. 2, it will be seen that the rigid supporting block 33 is provided with an enlarged horizontal bore 54 intermediate its length, and projecting through said bore is a shaft 55 having its rearward end joined to the aforementioned crossbar 44. The forward end of said shaft 55 is threaded as at 55' and has a knurled wheel 56 thereon adapted to abut against the plate 34 covering the front face of said supporting block. A coil spring 57 surrounding said shaft 55 yieldably urges the slidable unit including the rods 43, central shaft 55, and crossbar 44 rearwardly to a position where the roller 45 carried by said crossbar pressurably bears against the aforementioned cam 25.

In the operation of the present invention, and with reference now more particularly to the wiring diagram illustrated in FIG. 4 of the drawing, when the switch is turned on the magnetic clutch ll of the timer initiates the timing motor 12, as hereinabove described. After a preset time delay the switch 21 closes, thereby energizing the drive motor 23.

As the drive motor shaft 24 (FIG. 1) turns, the drive cam turns therewith, the function of which will be hereinafter seen, and simultaneously the adjacent cam 31 on said shaft rotates to actuate the microswitch 32. The normally open NO contacts of said microswitch 32 are in series with the magnetic clutch ll of the time delay switch, and at the beginning of the timing cycle the NO contacts of said switch 32 are closed by the cam 3i so that said magnetic clutch 11 and timing motor 12 are operative. As said cam begins to turn, however, the NO contact of the switch 32 opens, disengaging the timing clutch l1 and resetting the timer. At the same time the switch 32 NO contacts open, the NC contacts of said switch close, so that the drive motor 23 continues to run until the cam 31 again opens the NC contacts of said switch, thereby shutting off the drive motor 23 and closing the switch NO contacts. Thus the magnetic clutch M is reenergized to again start the timing cycle.

With reference now to FIGS. 1 and 2 of the drawing, when the driving motor 23 is actuated as hereinabove described, the cam 25 associated therewith begins to turn and push forwardly (to the left in the drawing) against the roller assembly 45 carried by the movable unit including the cross arm 44, said unit being pressurably retained in firm engagement with said cam 25 by the spring 57 (FIG. 2). As said movable unit moves forwardly the rods 43 thereon function to push the plungers 50 axially inwardly within the syringes 51, thereby forcing the flushing fluid contained in said syringes into the cannulae (not shown) with which said syringes communicate. Said flushing fluid effectively purges the cannulae of any blood clots forming therein, and maintains the lumen of said cannulae free and unobstructed.

The travel distance, or stroke length, of the unit including said plunger-actuating rods 43 can be adjusted and set by manually turning the aforementioned knurled wheel 56. By limiting the plunger stroke length a smaller volume of fluid will be discharged into the cannulae. In the preferred embodiment of the invention said stroke length is variable between 0.2 to 2.0 millimeters, thereby allowing the apparatus to be used with very small children, where fluid volume is critical, as well as with adults where larger volumes can be tolerated.

After the syringes 5 I have been emptied the continued turning movement of the cam 25 permits the spring 55 to return the plunger-actuating unit to its initial position. During such return travel the rods 43 withdraw the plungers 50 relative to the syringes, thereby causing said syringes to again fill with flushing fluid supplied by an adjacent container. Although it is not shown in the drawings, in accordance with the preferred form of the present invention the fluid container or reservoir is formed of a flexible plastic bag mounted adjacent the machine and connected to the syringe by suitable tubing. Unlike conventional rigid containers, such a flexible bag is designed to be air free and to collapse when empty, thereby eliminating the possibility of air being inadvertently drawn into the syringe and directed into the patients bloodstream.

As is well known in the art, a double-acting one-way valve (not shown) is utilized in the end of the syringe to permit flushing fluid to selectively flow from the reservoir when the plunger is retracted, and into the cannulae when the plunger moves axially inwardly, thus providing the necessary pump action.

At the moment the plungers 50 are fully retracted and the syringes 51 have been refilled with fluid, the synchronized cam 31 engages the switch 32 to shut off the drive motor 23 until the preset timing mechanism again energizes the same. AS hereinabove described, said time interval can be any desired period, depending upon the requirements of the particular installation. Ordinarily, if a venous line is being maintained, relatively infrequent flushing is necessary, while the arterial cannulae require flushing at more frequent intervals.

Although the present invention is electrically powered, the only portion of the apparatus that actually comes in contact with the patient is the plastic syringe 51. Since plastic is a nonconductor there is no chance of the patient accidentally receiving an electric shock. A further important feature of the invention is that said plastic syringes 51, as well as the plastic tubing (not shown) used to connect the same to the fluid reservoir, are standard items readily available in a hospital, thereby facilitating maintenance and replacement as well as minimizing costs.

Another important feature of the present apparatus is that is produces a minimal distortion of the patients blood pressure for only about 2 seconds out of every 3 or 4 minutes. The result is greatly increased accuracy in monitoring vascular pressures as compared to prior automatic flushing systems wherein continuous flushing fluid pressure and flow is employed to maintain open cannulae. Moreover, with the present invention it is unnecessary to periodically fill the cannulae with an anticoagulant, as is frequently done in conventional flushing operations and which is definitely undesirable with postoperative patients.

Referring once again to the circuit diagram illustrated in FIG. 4 of the drawings, the relay 17 acts as a latching relay when energized by the above-mentioned auxiliary push button switch 41 mounted in the front plate 34 (FIGS. 1 and 2). Said relay actuates the drive motor 23 and causes it to continue to run until the relay is unlatched by the action of the cam 31 and shut off switch 32, as described. Thus it will be seen that the present machine can be operated independently of the automatic timing mechanism by means of the pushbutton switch 41. This is an important feature in the event a sudden clotting or clogging of a cannula necessitates immediate flushing action.

In addition to said auxiliary switching mechanism, supplemental relays can be readily operatively associated with the present apparatus for many diverse purposes. Such a relay could be used, for example, for the interconnection of a high limit alarm to automatically indicate when the patient is having a blood pressure problem, or other alarm or monitoring devices could be readily added.

From the foregoing detailed description it will be seen that the present invention provides a novel power-driven apparatus for automatically periodically flushing cannulae in patients blood vessels to prevent blood from clogging therein, which automatic device has a number of advantages over conventional cannulae-flushing means. Said apparatus not only eliminates the necessity for a nurse manually performing the flushing operation, thereby greatly promoting efficiency, but said automatic device makes it unnecessary to disturb the patient every few minutes, as is required with manual flushing.

A further advantage of the automatic cannulae-flushing apparatus comprising the present invention is that although the machine is electrically operated there is no chance of the patient accidentally receiving an electric shock therefrom. In addition, said apparatus utilizes standard disposable plastic syringes and tubing, such as are readily available in hospitals, thereby minimizing costs, and when used in conjunction with a collapsible fluid reservoir there is no chance of air being drawn into the system. Moreover, the invention is relatively simple in design and operation, and it is rugged and long-lasting in construction.

It is to be understood that while a preferred form of the invention has been illustrated and described herein, numerous variations or modifications thereof are possible. What is intended to be covered is not only the illustrated embodiment of the invention but also any and all forms thereof as may come within the spirit of said invention, and within the scope of the following claims.

What I claim is:

l. A cannulae-flushing apparatus, comprising: a base; a manually adjustable timer and electric switch device; a motor on said base operatively associated with said timer switch device and adapted to be energized thereby at preset time intervals, said motor having a drive shaft; a driving cam mounted fast on said motor drive shaft, a rod-supporting element mounted on said base; a plurality of elongated horizontal rods axially movably canned by said rod-supporting element, each of said horizontal rods having a rearward end and a forward end; cam-engaging means associated with said axially movable rods; spring means yieldably maintaining said camengaging means in pressurable engagement with said driving cam; a syringe holder mounted on said base forwardly of said axially movable rods; a plurality of syringes having a quantity of flushing fluid therein removably horizontally supported by said syringe holder and adapted to communicate with cannulae in patients arteries; a plunger axially movably carried in each of said syringes and projecting rearwardly therefrom; means on the forward ends of said axially movable rods removably securing the same to the rearward, projecting ends of said syringe plungers, whereby when said driving motor is energized the driving cam thereon turns and urges said axially movable rods forwardly to push said plungers axially inwardly in the syringes, thereby discharging flushing fluid into a cannulae with which said syringe is in communication to purge any blood clots forming therein, the continued rotation of said driving cam causing said spring-loaded rods to move rearwardly to their initial position while retracting said plungers to a position wherein said syringes can be refilled with flushing fluid; means for adjusting the stroke length of said axially movable rods to vary the quantity of flushing fluid discharged from said syringes, depending upon the requirements of the particular patient; a shutoff switch associated with said motor; a shutoff cam mounted fast on the motor drive shaft positioned to engage and actuate said shutoff switch when said syringe plungers have been fully retracted to turn off said driving motor, said motor remaining in an off condition until again automatically energized by the aforesaid timer switch device after a preset time interval; and auxiliary manual switch means for energizing said driving motor independently of said timing and automatic switch means. 

1. A cannulae-flushing apparatus, comprising: a base; a manually adjustable timer and electric switch device; a motor on said base operatively associated with said timer switch device and adapted to be energized thereby at preset time intervals, said motor having a drive shaft; a driving cam mounted fast on said motor drive shaft, a rod-supporting element mounted on said base; a plurality of elongated horizontal rods axially movably canned by said rod-supporting element, each of said horizontal rods having a rearward end and a forward end; cam-engaging means associated with said axially movable rods; spring means yieldably maintaining said cam-engaging means in pressurable engagement with said driving cam; a syringe holder mounted on said base forwardly of said axially movable rods; a plurality of syringes having a quantity of flushing fluid therein removably horizontally supported by said syringe holder and adapted to communicate with cannulae in patients'' arteries; a plunger axially movably carried in each of said syringes and projecting rearwardly therefrom; means on the forward ends of said axially movable rods removably securing the same to the rearward, projecting ends of said syringe plungers, whereby when said driving motor is energized the driving cam thereon turns and urges said axially movable rods forwardly to push said plungers axially inwardly in the syringes, thereby discharging flushing fluid into a cannulae with which said syringe is in communication to purge any blood clots forming therein, the continued rotation of said driving cam causing said spring-loaded rods to move rearwardly to their initial position while retracting said plungers to a position wherein said syringes can be refilled with flushing fluid; means for adjusting the stroke length of said axially movable rods to vary the quantity of flushing fluid discharged from said syringes, depending upon the requirements of the particular patient; a shutoff switch associated with said motor; a shutoff cam mounted fast on the motor drive shaft positioned to engage and actuate said shutoff switch when said syringe plungers have been fully retracted to turn off said driving motor, said motor remaining in an off condition until again automatically energized by the aforesaid timer switch device after a preset time interval; and auxiliary manual switch means for energizing said driving motor independently of said timing and automatic switch means. 